Speaker
Description
LTX-β: Plasma Control System Hardware and Software Design
Keith Erickson, Ricardo Shousha, Dennis Boyle, Enrique Merino, Richard Majeski
To advance the operating envelope of the Lithium Tokamak Experiment-Beta (LTX-β) [1-3] at the Princeton Plasma Physics Laboratory (PPPL), a sophisticated real-time feedback control system is required to handle 135 kA plasma currents and 700 kW neutral beam injection [4]. This work presents a cost-effective Plasma Control System (PCS) designed by leveraging technologies shared across several tokamaks to maximize deterministic capabilities.
The hardware architecture centers around a Concurrent Real-Time iHawk host computer executing a RedHawk Linux real-time operating system kernel. Real-time data acquisition is achieved using 64-channel, 18-bit SAR digitizers sampling at 500 kHz, providing deterministic acquisition in batches every 32 μs. This oversampling strategy allows for real-time digital filtering to feed a stable active control loop with flexibility of shot cycle duration. To preserve legacy diagnostic assets safely, custom isolated junction boxes with specialized twisted-pair passive shielding were engineered to split analog signals, duplicating live sensor data into the real-time architecture without compromising existing offline data systems.
On the software layer, real-time diagnostic and execution handling combine the Scalable Hardware I/O Execution Layer for Diagnostics (SHIELD) platform with the General Atomics Plasma Control System (GA PCS). Feedback algorithms couple the GA PCS directly with the tokamak power supply controllers, while post-shot archiving is pushed to the existing MDSplus infrastructure now backed by an enterprise SAN deployment. The engineering execution, signal topology mappings, and preliminary loop latencies of this integrated stack are discussed.
This work was supported by the U.S. Department of Energy under contract number DE-AC02-09CH11466. The United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.
[1] D.P. Boyle et al., Nuclear Fusion 63 056020 (2023)
[2] A. Maan, et al., Physics of Plasmas 31, 022505 (2024)
[3] R. Shousha et al., Nuclear Fusion 65, 116009 (2025)
[4] R. Shousha et al., Fusion Engineering and Design (submitted)